For more information on species differences in immune cells see these publications and others:

Mestas J, Hughes Of mice and not men: differences between mouse and human immunology. Immunol. 2004 Mar 1;172(5):2731 8CC.

Weinberg JB, Misukonis MA, Shami PJ, Mason SN, Sauls DL, Dittman WA, Wood ER, Smith GK, McDonald B, Bachus KE, et al Human mononuclear phagocyte inducible nitric oxide synthase (iNOS): analysis of iNOS mRNA, iNOS protein, biopterin, and nitric oxide production by blood monocytes and peritoneal macrophages. Blood. 1995 Aug 1;86(3):1184-95.

Rotoli BM, Dall'asta V, Barilli A, D'Ippolito R, Tipa A, Olivieri D, Gazzola GC, Bussolati O. Alveolar macrophages from normal subjects lack the NOS-related system y+ for arginine transport. Am J Respir Cell Mol Biol. 2007 Jul;37(1):105-12. Epub 2007 Mar 15.